It is commonly known that the cultivation and harvesting of food crops and forest products results in the production of vast quantities of organic waste or biomass. It is also commonly known that biomass may be decomposed at high temperatures and in a reduced-oxygen setting in a reaction known as pyrolysis. Pyrolysis results in the release of volatile gasses and a residual solid material known as biochar. When the volatile gasses are condensed, a high-energy-content oil, called bio oil, is produced. Any remaining gas, called synthesis gas, is composed primarily of hydrogen and carbon monoxide, with small amounts of methane gas. Biochar, when used as a soil additive, provides a habitat for fungi and microorganisms beneficial to plant growth, stores moisture, decreases soil erosion, and decreases fertilizer runoff. Bio oil has a high BTU content, can be converted directly into electricity in petroleum-based power plants, and can be refined into diesel fuel. Very pure synthesis gas can be burned in a manner similar to natural gas, while less pure synthesis gas can still be burned for heat.
It is further commonly known that the typical pyrolysis reaction takes place at a location remote from that of the collection of the biomass consumed in the reaction. Once collected, the biomass is typically transported to a facility that either chips, grinds or otherwise fragments the biomass, and then the fragmented biomass is generally transported to the pyrolysis reaction site. The biomass fragments may then be augured into a pyrolyzing chamber. The auger provides a seal against oxygen to prevent combustion in the pyrolyzing chamber. The biochar and volatile gasses produced from the pyrolysis reaction rise within the pyrolyzing chamber until they are extracted. The biochar may be allowed to cool and is collected. The volatile gasses may be condensed and the resulting bio oil and synthesis gasses may be burned to provide the heat that drives the pyrolysis reaction. The collected biochar may then be transported to a field, orchard, packaging facility or other application. The typical biochar generation method, therefore, is inefficient in that energy must be consumed in the collection of the biomass, in the transportation of the collected biomass to the fragmentation site, in the fragmentation of the biomass, in the transportation of the fragmented biomass to the pyrolyzing chamber, in generating the heat that drives the pyrolysis reaction, and in the transportation of the biochar, bio oil and synthesis gasses to their ultimate applications.
FIG. 1 illustrates a schematic diagram depicting the typical biochar generation process known in the prior art. From the start (Block 201), biomass, in this example wood, is transported by truck to a biochar generation facility and then deposited in a storage area at Block 202. The biomass is moved to a biomass fragmenter, in this example a chipper, at Block 203. At Block 204, the fragmented biomass is fed into an auger. The fragmented biomass passes from the auger into the pyrolysis chamber at Block 205. Heat is introduced into the pyrolysis chamber at Block 206. Vaporized synthesis gasses and vaporized bio oil exit the pyrolysis chamber and enter the vapor condenser at Block 207. The condensed synthesis gasses are filtered at Block 208 and then fed back into the heater at Block 206. The condensed bio oil is collected at Block 209 and is transported by truck for refining or other use at Block 213. The biochar passes through the char spout at Block 210, is collected at Block 211 and is allowed to cool in the biochar cooling area at Block 212. The cooled biochar is then transported by truck for ultimate application at Block 214.
There are numerous devices that have attempted to provide a biochar generator. For example, U.S. Pat. No. 7,322,301 to Childs, discloses a system and method for processing sewerage sludge and other organic based feedstocks, in an energy efficient manner that minimizes or eliminates unwanted byproducts, including pathogens, and generates useful environmentally safe products. The sewage sludge or other feedstocks are partially dried before being input to a gasifier operating under partial pyrolitic conditions with a small amount of oxygen or air present to produce fuel in the form of synthesis gas, bio-oil fuel and char. A small percentage of the fuel may be used to maintain the operation of the feedstock drying process after it is started and a small amount of the synthesis gas produced in the gasifier reacts with the small amount of oxygen present with the feedstock to maintain the pyrolysis temperature in the gasifier in order to make the system economically viable.
U.S. Published Patent Application No. 2008/0006520 by Badger et al., discloses a system for the conversion of carbonaceous feedstocks into useful sources for energy, chemicals, or other materials including a dryer into which the carbonaceous feedstock is placed and a reactor chamber in communication with the dryer for receiving the dried feedstock. The system also includes a heat carrier for further processing of the feedstock in the generation of useful sources of energy, chemicals or other material. The system further includes a char separation and recovery mechanism linked to the reactor chamber for separating char produced as a result of processing of feedstock within the reactor chamber from the heat carrier. The system still further includes a condenser to recover a liquid product condensed from the gas and vapor, and a furnace for burning char as needed for operation of the disclosed system.
U.S. Published Patent Application No. 2007/0012232 by Skrypski-Mantele et al., discloses a system and method for thermal conversion of sludge into fuel and other products such as char without the creation of reaction water. The system and method disclosed allows for the independent control of mixing and the movement of sludge through pyrolysis systems.
U.S. Pat. No. 5,853,548 to Piskorz et al., discloses a thermolysis process for the production of volatiles for an external combustor or liquefaction of biomass solids. The thermolysis is carried out in a single fluidized bed of inert material operating at near atmospheric pressure, relatively low temperature, long residence times and moderate heating rates. The distribution of thermolysis products is among solid (char) and gases. The product effluent can either be quenched, to produce a high liquid yield in addition to a low char yield, or can be used in either the same combustor or a second combustor to produce heat energy. In using a quencher, the quenched liquid is of a similar composition to those obtained by a so-called fast pyrolysis process. The specified conditions are such as to allow production of liquids in high yields in an energy efficient manner. The low severity of the conditions allows simplified process design and scale-up leading to lower capital and operating costs as well as easier control.
U.S. Pat. No. 4,253,406 to Spitz et al. discloses a flueless portable primary combustion chamber forming part of a pollution control incineration system having an elongated duct with one or more inlets positioned at or near grade level. An upright standpipe covers an inlet opening to provide a polluted gas inlet to the duct from a location elevated above grade. The portable primary combustion chamber is constructed with a closed top and an open bottom which overfits the standpipe in a manner to allow combustible material to be burned within the shell and to direct combustion gases downwardly into the duct through the top of the standpipe.
Additionally, the pyrolysis reaction can be modified to alter the various products that may be produced in the pyrolysis chamber. The pyrolysis reaction produces biochar, bio oil and synthesis gases. The amount and composition of the various products can be changed by modifying the conditions of the pyrolysis chamber. Therefore, there exists a need to provide a biochar generator that is adapted to modify the conditions of the pyrolysis chamber to produce biochar, bio oil and synthesis gases in the amount or ratio desired. There is also a need to modify the conditions of the pyrolysis chamber to alter the composition of the output products.